Police have not named the dead gunman, 45, but say he has no ties to terror or subversive groups.
Police responded to the call about 8 a.m. at Fiamma Inc., which makes accessories for recreational vehicles, Orange County Sheriff Jerry Demings said. The business is located in an industrial area northeast of downtown.
Three men and a woman were found dead at the scene, Demings said. Another man died at Orlando Regional Medical Center.
Seven others were inside the business when the shootings took place.
‘My boss is dead’
Shelley Adams told reporters she spoke Monday with her sister, who works at Fiamma and was in the restroom when she heard a noise.
Her sister came out and saw someone lying on the floor.
“She said, ‘I saw too much. My boss is dead,'” Adams said.
Shooter was fired this year
The gunman was fired from Fiamma in April, Demings said.
He had a minor police record including arrests for DUI and marijuana possession.
Police had responded to a battery complaint against him at Fiamma in 2014. The victim of that incident was not among the dead Monday, Demings said.
Pulse anniversary approaches
Almost a year ago, Orlando was the site of the nation’s worst terror attack since 9/11. On June 12, 2016, a gunman killed 49 people at the Pulse nightclub.
“Over the past year, the Orlando community has been challenged like never before,” Florida Gov. Rick Scott said in a statement Monday.
“I will remain in contact with the Orlando law enforcement community throughout the day as more information is made available,” Scott said.